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New contrast agent infiltrates aorta

BioPhotonicsAug 2006
Despite recent advances in detection
and treatment, atherosclerosis — characterized by deposits in the inner layers
of arteries — is still a major health concern worldwide. Noninvasive detection
and characterization of the plaques associated with the condition could contribute
to a drop in morbidity and mortality. Contrast-enhanced MRI has shown potential,
for example. However, most of the currently available contrast agents do not deliver
sufficient gadolinium to the arterial wall for this purpose.

Investigators have come up with a number of ways
to address this limitation, including incorporating the agents into linear polymers,
dendrimers and protein-bound chelates to increase the effective local concentration.

In a Nano Letters paper published
online on July 26, researchers with The Mount Sinai School of Medicine and with
New York University School of Medicine, both in New York, and with Thomas Jefferson
University in Philadelphia reported a family of high-density lipoproteinlike nanoparticle
contrast agents that they had developed.

They noted several advantages of this
platform. For example, the nanoparticles are small enough to cross the endothelium
to enter and exit plaques, but large enough to allow attachment of sufficient amounts
of MRI contrast materials. Also, the protein components of the agents are biodegradable
and do not cause immunoreaction.

The scientists tested the agent by
injecting it into mice with accelerated plaque progression and by imaging the abdominal
aorta of the mice with a 9.4-T MR system made by Bruker Instruments of Billerica,
Mass. The experiments showed that the agent localized predominantly in the plaques;
there was no contrast-enhanced MR signal in control mice with no arterial lesions.
Thus it may eventually contribute to improved detection and treatment of atherosclerosis.

The contrast agent was designed to
work not only with MRI, but also with computed tomography and near-infrared imaging.
In addition, investigators could modify its protein components to target different
receptors or other parts of the plaques.